The discovery of stem/progenitor cells within germinal zones of the mammalian brain has led to the development of a field of neurobiology that deals with the potential of these cells to repair compromised or diseased regions of the brain. Many neurodegenerative diseases affect white matter specifically, and so are concerned with reconstituting the oligodendrocyte lineage in affected brains. We have identified the inherited pediatric leukodystrophy Canavan disease (CD) as a potential candidate for cell-based therapy. CD is caused by inactivating mutations to the oligodendrocyte- specific enzyme aspartoacylase (ASPA) and is characterized by a progressive decrease in CNS white matter by an as yet unknown mechanism. Studies performed in an ASPA- null animal model of CD by our laboratory have demonstrated dysregulated oligodendrocyte development in vivo that results ultimately in a significantly reduced number of late-stage oligodendrocytes. These studies provide a foundation for the comprehensive analysis of the potential of cell-based therapy for CD. The study proposed here seeks to provide proof-of-principle evidence to support the development of such a therapy, and will systematically analyze the receptivity of the ASPA-null tremor rat brain to repopulation by neurosphere-forming cells generated from neonatal GFP- transgenic donor rats that have been characterized by our laboratory. We are proposing to transplant GFP-transgenic cells into ASPA-null tremor rats and analyze transplanted cell engraftment, survival, and myelination using unbiased stereology. This analysis will be complemented by the testing of motor performance in transplanted animals, thereby allowing a statement to be made regarding the relationship between robust, quantitative stereological endpoints and the potential of cell-based therapy to promote phenotypic rescue in an animal model of CD. This study is anticipated to provide valuable data regarding the receptivity of the specific in vivo microenvironment to this form of therapy, and will enable statistically valid estimates of the degree of remyelination required to impact the phenotype. PUBLIC HEALTH RELEVANCE: This proposal details a study designed to generate proof-of-principle data to support the development of a cell-based therapy for Canavan Disease. This study is anticipated to provide valuable in-vivo data to assess the degree of remyelination required to impact the phenotype. Efficacy data collected in this study will constitute a significant part of the pre- requisite preclinical studies for submission of an Investigational New Drug Application to the FDA to evaluate the effect of a human Neural Stem Cell Therapy in Canavan patients.